A patterned sapphire substrate (PSS) is a sapphire substrate with a patterned surface formed via photoetching and etching. The patterned substrate, on the one hand, can effectively reduce dislocation density of the epitaxial structure and improve lattice quality and evenness of the epitaxial material, thereby improving the internal quantum light-emitting efficiency of the light-emitting diode; on the other hand, the pattern structure increases light scattering and changes light route of the light-emitting diode, thus optimizing light extraction chance.
The width of the PSS pattern bottom has certain influence on the light extraction efficiency of the substrate: the wider the bottom is, the larger the pattern surface area is, and therefore the larger the light reflection region is and the higher the light extraction efficiency is. Meanwhile, space between adjacent patterns also has certain influence on the growth of the subsequent epitaxial layer: if space is too small, the inside defect in the formed epitaxial layer increases, which is to the disadvantage of the light extraction of the semiconductor element; and if space is too large, it would lead to a small number of substrate patterns arranged on the substrate surface of same size, thus decreasing substrate light extraction efficiency. Therefore, how to obtain a substrate pattern with appropriate density and large bottom width is one of the key technologies to improve light extraction efficiency of the semiconductor element.